The quantitative determination of analytes in body fluids is of great importance in the diagnoses and maintenance of certain physical conditions. For example, blood glucose, hemoglobin (Hb), hemoglobin A1c (HbA1c), lactate, cholesterol, bilirubin, and other analytes should be monitored in certain individuals. Individuals with low blood glucose levels may need medical attention. In particular, it is important that individuals who have diabetics frequently check the glucose level in their body fluids because such individuals may become ill if their blood glucose level becomes too high—a condition known as hyperglycemia. The results of these analyte tests may be used to determine what, if any, insulin or other medication should be administered.
The analyte concentration tests are typically performed using optical or electrochemical testing methods. In the embodiments employing an electrochemical method, a test sensor contains biosensing or a dry reagent layer that reacts with, for example, blood glucose. A testing portion of the test sensor contains the dry reagent layer and is adapted to receive a fluid (e.g., blood) being tested that has accumulated on, for example, a person's finger after the finger has been pricked. The fluid is typically drawn into a channel that extends from an end or side of the test sensor to at least the dry reagent layer, located in the testing portion. In certain embodiments, the test sensor draws the fluid into the channel using capillary action so that a sufficient amount of fluid to be tested is drawn into the test sensor's testing portion. The fluid then chemically reacts with the dry reagent layer in the testing portion. This results in an electrical signal, indicative of the glucose level in the fluid, being supplied to electrical contact areas, which are typically located at a second opposing end near the rear or contact portion of the test sensor.
The test sensor's accuracy and precision depend on the uniform consistency of the dry reagent layer's physical structure and chemical composition. To ensure good precision and accuracy, from test sensor to test sensor, the dry reagent layer should have little variation not only in quantity, but also in physical structure. Thus, it is desirable for the reagent material to be deposited as a wet reagent droplet having substantially uniform height, radius, and contact angle from test sensor to test sensor such that when the wet reagent droplet dries a dry reagent layer is formed. However, the wet reagent droplet is typically deposited on a conductive-covered polymeric substrate (e.g., a gold PET substrate). Such substrate surfaces tend to always contain surface variations or surface irregularities. These surface variations may be caused by contamination on the deposition surface, irregularities of the electrode pattern surface, or irregularities of the polymeric substrate, which all make it difficult to deposit a structurally uniform wet reagent droplet from test sensor to test sensor.
It would be desirable to overcome the above-noted problem of surface variations, while providing a precise, rapid, and accurate method of depositing uniform wet reagent droplets from test sensor to test sensor.